Warnings: Global warming could lead to a catastrophe for humankind in 2100

09/06/2017

Under a dual onslaught of
global warming and localised, urban heating, some of the world's cities may be
as much as eight degrees Celsius (14.4 degrees Fahrenheit) warmer by 2100,
researchers warned on Monday. Such a temperature spike can have dire
consequences for the health of city-dwellers, robbing companies and industries
of able workers, and put pressure on already strained natural resources such as
water.

The projection is based
on the worst-case-scenario assumption that emissions of planet-warming
greenhouse gases continue to rise throughout the 21st century.The top quarter of most
populated cities, in this scenario, could see the mercury rise 7 C or more by
century's end, said a study in the journal Nature Climate Change.

For some, nearly 5 degrees
of the total would be attributed to average global warming. The rest would be
due to the so-called Urban Heat Island (UHI) effect, which occurs when cooling
parks, dams and lakes are replaced by heat-conducting concrete and asphalt —
making cities warmer than their surrounds, the researcher said.

"The top five
percent (of cities per population) could see increases in temperatures of about
8 C and larger," study co-author Francisco Estrada of the Institute for
Environmental Studies in the Netherlands told AFP.

Estrada and a team used
different projections of average planetary warming, combined with the UHI
effect and potential harms, to estimate the future costs of warming on cities.

The median city, right in
the middle of the range, stands to lose between 1.4 and 1.7 percent of GDP per
year by 2050 and between 2.3 and 5.6 percent by 2100, they concluded. "For
the worst-off city, losses could reach up to 10.9 percent of GDP by 2100,"
wrote the team.

UHI
"significantly" increases city temperatures and economic losses from
global warming, they added. This meant that local actions to reduce UHI — such
as planting more trees or cooling roofs and pavements, can make a big
difference in limiting warming and minimising costs.

Cities cover only about
one percent of earth's surface but produce about 80 percent of gross world
product and account for around 78 percent of energy consumed worldwide, said
the researchers. They produce more than 60 percent of global carbon dioxide
emissions from burning coal, oil and gas for fuel.

The world's nations
agreed in Paris in 2015 to the goal of limiting average global warming to two
degrees Celsius over pre-Industrial revolution levels by curbing greenhouse gas
levels in Earth's atmosphere. For the latest study, researchers used data from
the world's 1,692 largest cities for the period 1950 to 2015.

A report by a leading research body
monitoring the Arctic has found that previous projections of global sea level
rise for the end of the century could be too low, thanks in part to the pace of
ice loss of Arctic glaciers and the vast ice sheet of Greenland. It’s just the
latest in a string of cases in which scientists have published numbers that
suggest a grimmer picture than the one presented in 2013 by an influential
United Nations body, the Intergovernmental Panel on Climate Change.

The
assessment found that under a relatively moderate global warming scenario — one
that slightly exceeds the temperature targets contained in the Paris climate
agreement — seas could be expected to rise ‘‘at least’’ 1.7 feet by the year
2100. Under a more extreme, ‘‘business as usual’’ warming scenario, meanwhile,
the minimum rise would be 2.4 feet.

The new
findings were published as part of a broader overview report by the Arctic
Monitoring and Assessment Program, a working group of the intergovernmental
Arctic Council, which unites eight Arctic nations, including the United States,
and six organizations representing the indigenous peoples of the Arctic. It is
the work of 90 scientists and 28 peer reviewers.

The
report bluntly contrasts its sea level findings with a previous 2013 report
from the UN Intergovernmental Panel on Climate Change, which had put the
‘‘likely’’ low end sea level rise number for these two scenarios at about 1
foot and 1.5 feet for the period between 2081 and 2100. That global body —
whose high-end sea level rise number for the year 2100 was just shy of 3.2 feet
— has often seen its assertions on sea level rise faulted by scientists for
being too conservative.

An
influential study of Antarctica published last year in the journal Nature
suggested that the frozen continent alone could nearly double the IPCC’s sea
level projections for the end of the century.

(The IPCC
did concede that sea levels could be higher than its ‘‘likely’’ forecast in the
event of a ‘‘collapse of marine-based sectors of the Antarctic ice sheet’’ —
but it added that ‘‘there is medium confidence that this additional
contribution would not exceed several tenths of a meter of sea level rise
during the 21st century.”)

And since
then, several other scientific documents — presumably aware of this Antarctic
research — have cited the possibility of particularly extreme sea level rise by
2100, even if they cannot necessarily quantify the likelihood of it occurring.

‘‘These estimates of higher sea level
contributions from the Arctic will only add to the new, higher estimates of
potential sea level contributions from Antarctica — which is not good news,’’
said Rob DeConto, a geoscientist at the University of Massachusetts at Amherst
who published the aforementioned Antarctica study and also worked on the
California study. He was not involved in the new Arctic report.

The
Arctic report states that Greenland, in particular, lost 375 billion tons of
ice per year from 2011 through 2014, enough to single-handedly raise the global
sea level by about a millimeter per year. That annual loss, the document
states, is ‘‘equivalent to a block of ice measuring 7.5 kilometers or 4.6 miles
on all sides.’’

Because
of the difference between the worst case and more moderate sea level rise
scenarios, the report concludes that the Paris climate agreement could
substantially reduce the global sea level rise seen by 2100, even though seas
will still rise considerably under any scenario.

‘‘You
have to have a deliberate and sustained implementation of Paris for 30 years
before you see a significant difference in the rate of global sea level rise,’’
Colgan said.

The Trump
administration’s irresponsible decision of withdrawing from Paris accord would
make the situation worse and push the world closely to the biggest catastrophe
in the humankind’s history. How can they continue calling for human rights and
democracy while they are getting more extreme and conservative in protecting
their benefits with the selfish policy of “America first”./.

Chia sẻ bài viết ^^

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Such a rise – which would be much higher nearer the poles – would have cataclysmic and irreversible consequences for the Earth, making large parts of the planet uninhabitable and threatening the basis of human civilisation.